1. Field of the Invention
This invention relates to a method for forming etched patterns which are used for example in the process of manufacturing semiconductor elements.
2. Description of the Prior Art
A prior method of forming fine etched patterns is shown in FIGS. 1 to 4. In this prior example, when, as shown in FIG. 1, a polycrystalline silicon layer 2 formed on a silicon oxide layer 1 is to be worked to a fine pattern, after coating a positive photoresist 3 onto the polycrystalline silicon layer 2, the photoresist 3 is exposed to light as indicated by arrows 4, through a predetermined photo-mask (not shown), at portions corresponding to the fine pattern. This is then chemically developed so that only the hardened photoresist 3 in those portions exposed to the light remains. Then, with this photoresist 3 as a mask, the aforementioned polycrystalline silicon layer 2 is etched away as shown in FIG. 3, and by chemically removing the remaining photoresist 3, a desired fine pattern as shown in FIG. 4 is formed in the polycrystalline silicon layer 2.
However, this prior method of fine pattern forming has drawbacks in that it involves many steps, and has a tendency to become complicated because of the use of a photoresist as the pattern etching mask, and further, as can be seen in FIG. 2, the exposure to light and developing of the photoresist produce dimensional errors in the pattern obtained, because the resist pattern formed is not very sharp or well defined, and so there are limits to the fineness, and there is the problem of contamination that accompanies the chemical treatment of using a resist, etc.